In cyclic systems there is often a need for recording measured values in parallel, i.e., more or less simultaneously, for control. Measured values dependent on the control put high demands on measured value processing. Traditional methods which operate using analog filters, for example, are difficult to implement. Their configuration is static and cannot be adjusted during operation. Although this situation may be improved by using sample elements and hold elements, in systems in which the control constantly changes and/or in which an additional, possibly varying interference signal is superimposed on the measured signal, the configuration options of the measuring environment using sample and hold elements are limited.
In controlling an electric motor, in particular in the case when the coasting voltage is measured in generator operation of DC motors, there is the problem that in conventional methods the influence of speed-dependent interference signal components is relatively great.